Home gardens are by far the biggest source of food in cities and towns for pollinating insects, including bees and wasps, according to new research.
The study, led by the University of Bristol and published on Sunday in the Journal of Ecology, measured for the first time how much nectar is produced in urban areas. It also found out more on how far residential gardens accounted for the vast majority of this nectar, accounting for some 85% on average.
Results showed three gardens generated daily on average around a teaspoon of Nature’s ambrosia, the unique sugar-rich liquid found in flowers that pollinators drink for energy.
While a teaspoon may not sound much to humans, it is the equivalent to more than a tonne to an adult human and enough to fuel thousands of flying bees. The more bees and fellow pollinators can fly, the greater diversity of flora and fauna will be maintained.
Nicholas Tew, who is both the lead author of the study and working towards a PhD in Ecology, said, “Although the quantity and diversity of nectar have been measured in the countryside, this wasn’t the case in urban areas, so we decided to investigate.”
He added, “We expected private gardens in towns and cities to be a plentiful source of nectar, but didn’t anticipate the scale of production would be to such an overwhelming extent.”
Tew noted that the findings highlight the pivotal role private gardens play in supporting pollinators and promoting biodiversity in urban areas across the country.
The research was carried out in partnership with the Universities of Edinburgh and Reading, as well as the Royal Horticultural Society. It examined the nectar production in four major UK towns and cities, namely Bristol, Edinburgh, Leeds, and Reading.
Nectar production was measured in nearly 200 species of plant by extracting nectar from more than 3,000 individual flowers. The extraction process involves using a fine glass tube. The sugar concentration of the nectar was quantified with a refractometer, a device that measures how much light refracts when passing through a solution.
“We found the nectar supply in urban landscapes is more diverse, in other words, comes from more plant species, than in farmland and nature reserves, and this urban nectar supply is critically underpinned by private gardens,” said Tew.
“Gardens are so important because they produce the most nectar per unit area of land and they cover the largest area of land in the cities we studied.”
Nearly a third, or 29%, of the land in urban areas is comprised of domestic gardens, which is six times the area of parks, and 40 times the area of allotments.
“The research illustrates the huge role gardeners play in pollinator conservation, as without gardens there would be far less food for pollinators, which include bees, wasps, butterflies, moths, flies, and beetles in towns and cities,” Tew said, “It is vital that new housing developments include gardens and also important for gardeners to try to make sure their gardens are as good as possible for pollinators.”
He noted that ways to do this include planting nectar-rich flowers, and ensuring there is always something in flower from early spring to late autumn. Other means cover mowing the lawn less often to let dandelions, clovers, daisies and other plant flowers flourish, avoiding spraying pesticides which can harm pollinators, and avoiding covering the garden in paving, decking or artificial turf.
Stephanie Bird, an entomologist at the Royal Horticultural Society, which helped fund the research, said, “This research highlights the importance of gardens in supporting our pollinating insects and how gardeners can have a positive impact through their planting decisions.
She noted that gardens should not be seen in isolation, and instead, they are a network of resources offering valuable habitats and provisions when maintained with pollinators in mind.